Hello I am new to this forum and I need to find out if anyone knows if the speed sensor is located on the tranny or under the dash on the 1988 lesabre.

It is bolted to the back of the speedometer, right next to the speedo cable, with a harness to the speed buffer.

Unless you have an electronic speed sensor. in that case it is bolted on the top of the tranny on the passenger side with 4 wires coming out the back :).

yes it is electric. thanks alot everyone for your help with this.